Refrigerating device comprising a gas-refrigerator



June 3, 1958 K. ROOZENDAAL ET AL 2,836,964

REFRIGERATING DEVICE COMPRISING A GAS-REFRIGERATOR Filed Nov. 4, 1954 2 Sheets-Sheet 1 INVENTORS KLAAS ROOZENDAAL EVERT HELLINGMAN J1me 1958 K. ROOZENDAAL ET AL 2,836,964

REFRIGERATING DEVICE COMPRISING A GAS-REFRIGERATOR 2 Sheets-Sheet 2 Filed Nov. 4, 1954 Jill/O-MECV/Ak/JM INVENTORS AS ROOZENDAAL EVERT HELLINGMAN United rates atent @fiice REFRIGERATIN'G DEVICE COMPRISING A GAS-REFRIGERATGR Klaas Roozendaal and Evert Helllngman, Eindhoven, Netherlands, assignors, by mesne assignments, to North American Philips Company, Inc, New York, N. Y., a corporation of Delaware Application November 4, 1954, Serial No. 466,794

Claims priority, application Netherlands November 5, 1953 7 Claims. (Cl. 62-2) The invention relates to refrigerating devices comprising a gas-refrigerator by means of which an auxiliary medium provided in a pipe system can be condensed after which the condensate is evaporated in an evaporator, heat thus being Withdrawn from an object required to be cooled, While the produced vapour is returned to the gas-refrigerator.

The term gas-refrigerators as used herein means a refrigerator operating on the reversed hot-gas reciprocating engine principle. These refrigerators may be realised in various manners, for example, as a displacer engine, as a double-acting engine, or as an engine the working space of which is combined with that of a hot-gas reciprocating engine. These engines are adapted to produce cooling through a large temperature range. Thus, engines may, for example, be constructed which are adapted to produce cooling at a temperature of -40 C. However, the refrigerator may alternatively be constructed such as to produce cooling at a temperature of -80 C. or even of 200 C.

If the cooling produced by the gas-refrigerator is required to be used elsewhere, it will be possible in the above-described manner to convey this cooling elsewhere by means of an auxiliary medium.

In domestic refrigerators use is frequently made of a medium flowing in a closed pipe-system while by means of evaporation it withdraws heat from an object required to be cooled, after which the produced vapour is condensed. In these refrigerators use is frequently made of the so-called Freon 12 as a medium. In these domestic refrigerators there is generally a comparatively slight difference of, for example, 40 C. between the temperature of the evaporator, when the device is operative, and its temperature, when the device is inoperative, the lowest temperature of the evaporator being, for example, C.

However, if a refrigerating device comprises a gasrefrigerator which produces cooling at low temperatures, the cooling produced by the gas-refrigerator being conveyed elsewhere by means of an auxiliary medium, it has been found according to the invention that the auxiliary medium has to satisfy particular requirements due to the larger temperature differences. On the one hand it will be necessary for a sufiicient amount of condensate to be contained in the pipe-system at low temperatures of, for example, 80 C. or lower, while on the other hand it is desirable for the pressure prevailing in the pipe system not to be increased excessively, if the gas-refrigerator is rendered inoperative.

Hence, according to the invention as an auxiliary medium use is made of a vapour the boiling temperature of which is less than C. at a pressure of 20 atmospheres, while at 20 C. at a maximum 1 gram-molecule of the said auxiliary medium is contained in the pipe system per dmfi. As auxiliary medium use may, for example, be made of methane, ethane, nitrogen and CHFgCl.

of the pipe system takes part in the cycle.

In one embodiment of the invention the amount of condensate supplied to the evaporator is varied by variation of the cooling produced by the gas-refrigerator. The cooling produced by the refrigerator can be varied by turning on or turning off the refrigerator or by varying at least one of the following engine quantities, number of revolutions, pressure of the working medium, phase difference of the piston shaped members reciprocating in the engine or clearance of the engine.

In one embodiment of the invention the cooling produced by the gas-refrigerator is controlled in accordance with the temperature of the auxiliary medium.

In an alternative embodiment of the invention the cooling produced is controlled in accordance with the pressure of the auxiliary medium. According to a further alternative embodiment of the invention the cooling produced is controlled in accordance with the amount of condensate contained in the pipe system.

In a preferred embodiment of the invention the pipe system for the auxiliary medium comprises a space which is connected to this pipe system by means of an overflow and is arranged such that the condensate is supplied to this space if the liquid level rises at this overflow. The amount of condensate may, for example, be registered by a float device, While provision may be made of a mechanism which, when the liquid level rises, controls the gas-refrigerator in a manner such that the produced cooling is reduced.

An alternative very simple control is obtainable if in an alternative embodiment of the invention heat is supplied to the said space :so that the condensate contained in this space is again evaporated. In this method the cooling produced by the gas-refrigerator can be maintained constant if the amount of cooling which is withdrawn from the auxiliary medium in the evaporator varies. Heat can be supplied to this space in various ways, for example, by means of a helically wound electric heater filament.

In a preferred embodiment of the invention heat is supplied to the space by means of conduction through an element one end of which is at a temperature exceeding that of the condensate. This end might, for example, be in heat-exchanging contact with the atmospheric air. However, this method has a limitation in that boar-frost might settle on the element which would reduce the heat transfer to the element. Consequently, in a further embodiment of the invention it is desirable for one end of the element to be in heat exchanging contact with the cooling water of the refrigerator, so that the formation of hoar-frost or ice is avoided.

in a further embodiment of the invention the pipe system can be reduced during operation of the refrigerator with the result that a greater. amount of liquid per dm. When the engine is stopped, the pipe system has to be enlarged.

For this purpose the pipe system may be connected, when the refrigerator is stopped, to an auxiliary space by means of two pipes, one of which has a check valve arranged in it such that only auxiliary medium is allowed to flow to this space, a controllable stop valve being provided in the second part.

The invention will now be described with reference to the accompanying drawing, in which some embodiments thereof are shown by way of example, and in which Fig. 1 shows an embodiment in which the auxiliary circuit comprises an additional space in which an excess amount of condensate can be evaporated,

Fig. 2 shows an embodiment in which the volume of the auxiliary circuit can be enlarged by the addition of an auxiliary space, the amount of cooling produced by the gas-refrigerator being variable by variation of the number of revolutions;

The device shown in Fig. 1 comprises a gas-refrigerator I realised as a so-called displacer engine. This gasrefrigerator comprises a cylinder 2 in which a displacer 3 and a piston 4 reciprocate at a substantially constant phase difference. For this purpose the displacer is connected to a crank of a crank shaft 6 by means of a system of connecting rods, the piston being also connected to a crank of this crank shaft by means of a connecting rod system 7. The space 8 on top of the displacer 3 is the freezing chamber of the engine and this space is connected to a space 12, the so-called cooled chamber, by means of a freezer 9, a regenerator 10 and a cooler 11. The refrigerator is driven by an electric motor 13 The freezer 9 is enclosed in a space 14 in which an auxiliary medium can be condensed. The condensation product is collected in an annular channel 15 and can be conveyed to an evaporator 18 through a pipe 16' in which a pump 17 may be provided. The evaporator 18 is arranged in a space 19 which is required to be maintainedat a low temperature and which forms the object required to be cooled. The evaporated auxiliary medium is returned to the space 14 through a pipe 20; p I

Through an overflow constituted by the upper rim 21 of the annular channel 15 the space 14 is connected to an auxiliary space 22." This space 22 contains a number of fins 23 connected to a rod 24 made of conducive material, for example of copper. The bottom end 25 of the rod 24 is arranged in the supply-pipe 26 for the cooling Water. Thus, the pipe system of the device consists of the space 14 with the space 22, the pipe 16; the evaporator 18 and the pipe 20.

In this embodiment during normal operation the freezer of the gas-refrigerator is at a temperature of, for example,

-l2( C. In the pipe system use is made of an auxiliary medium the boiling temperature of which is less than 20 C. at a pressure of 20 kg./cm. for example methane; while at this temperature'the pipe system per dm.? contains at a maximum 1 gram-molecule of this auxiliary medium; If the temperature of the freezer of the gas-refrigerator during normal operation'is, for example, -l20 in this embodiment the pipe-system contains at a maximum 16 grams of methane per dmfi and if the volume of this system is, for example, 10 dmfi, the total amount of the medium'us'ed in the pipe-system is 160 grams:

The installation operates as follows: Before the device is started the pipe-system which, as has been mentioned hereinbefore, consists of the pipes 16 and 20, the spaces 14 and 22 and the evaporator 18 is filled with methane in a manner such that the system contains, for example,

0.6 gram-molecule or 9.6 grams per dm. In this event the pressure in the pipe-system is 14.5 kg./ cm.? at 20 C. If thereupon the gas-refrigerator is started, heat will be withdrawn from the auxiliary medium so that the temperature and the pressure of this auxiliary medium will fall off. This continues until a state of equilibrium is obtained between the amount of heat which is withdrawn from the medium by the gas-refrigerator and the amount of heat supplied to the auxiliary medium in the evaporator. When this state is obtained, a stationary state is reached, in which the temperature and the pressure of the auxiliary medium are fixed. However, if the amount of heat supplied to the evaporator were to be reduced, less vapour would be produced with the result that the amount of condensate would be increased while at the same time without further expedients due to the cooling produced by the refrigerator the condensate would be'reduced in temperature. However, provision of the space 22 allows of keeping the temperature of the auxiliary medium substantially constant, for in this event the excess amount of condensate flows into the space 22 over the rim 21. In this space 21 the condensate is in heat-exchanging contact with the fins 23 associated with the rod 24.- The bottom end 25 of this rod, which end is arranged in the coolingwater pipe 26, is at a comparatively high temperature with the result that heat is supplied to the condensate by means of the rod so that this condensate isevaporated. The produced vapour is re-condensed by the gas-refrigerator. Since in this embodiment part of the condensate is not evaporated in the evaporator but elsewhere, the temperature and the pressure of the medium donot vary or substantially do not vary.

Fig. 2 shows an alternative embodiment of a refrigerating device corresponding to the invention in which like elements are designated correspondingly. The device comprises a gas-refrigerator 1 in Which'an auxiliary medium is condensed, after which it flows through a pipe 16 to an evaporator 18 arranged in a space 19. The vapour produced in this evaporator is returned to the gas-refrigerator through a pipe 20 and re-condensed. Since the evaporator is arranged below the condensing space of the refrigerator, in this embodiment a circulating pump can be dispensed with.

Throughpipes 31 and 32 a space is:conuected to the pipe 20. The pipe 31 contains a check valve 33 arranged such that medium can only flow from the. pipe 20 to the space 30. The pipe 32 contains a stop valve 34 by which the connection of the space 30 to the pipe 20 can be interrupted. In addition, the pipe-system comprises a measuring device 35 adapted to measure either the temperature or the pressure of the auxiliary medium. A variation of the measured quantity enables the cooling produced by the refrigerator to be varied by means of servo-mechanisms 36 and 37, for example, by varying the speed of the motor 13 or the pressure of the working medium which runs in a closed cycle in the gas-refrigerator.

The installation operates as follows: before the refrigerator is put into operation the pipe-system consisting of the condensing space in the refrigerator 1, the pipe 16, the evaporator 18, the pipe 20 and the space 30 with the pipes 31 and 32, is filled with an auxiliary mediunn for example nitrogen, so that at room temperature the system contains at a maximum 1 gram-molecule of this auxiliary medium per drn. At the same time the stopvalve 34 is opened. When the gas-refrigerator is brought into ope f tion, the temperature and the pressure of the auxiliary"- medium will he reduced similarly to What has been described with reference to Fig. 1 until a state of equilibrium is obtained between the heat which is withdrawn from'thej medium by the refrigerator and the heat which is supplied to the auxiliary medium by means of the evaporator.

Thereupon the stop valve 34 can be closed so that the space 30 is no longer part of the'pipe system. Consequently, in this event the pipe system contains a greater amount of medium than would be desirable. in view of the pressure which is permissible in the pipe system at room temperature. If the gas-refrigerator is turned oif, the auxiliary space 30 will remain part of the pipe-system due to the provision of the check-valve 33, even if the stop-valve 34 is kept closed.

If during operation of the device the amount of heat supplied to the evaporator decreases, the pressure and the temperature of the system will be reduced similarly to what has been described hereinbefo-re. Due to the provision of the measuring device 35 and the servo-mechanisms 36 and 37 the cooling produced by the gasqefrigerator is reduced until the state of equilibrium is restored. Similarly to what has been described relatively to the speed it is also possible to reduce the pressure .of the working medium in the gas-refrigerator; for this purpose use can be made of the known devices for controlling the pressure in hot-gas reciprocating engines.

What is claimed is:

l. A refrigerating device comprising a cold gas refrigerator; a pipe system including an evaporator; a refrigerated space; and auxiliary medium circulating in said pipe system, said evaporator and part of said cold gas" refrigerator; said medium being condensed in said cold. gas refrigerator and supplied to said refrigerated space Where said condensate is evaporated and the evaporated auxiliary medium returned to communication with said cold gas refrigerator; said auxiliary medium being a vapor in at least part of the cycle and having a boiling temperature which is less than 20 C. at a pressure of approximately 20 atmospheres, while at a temperature of 20 C. said pipe system contains a maximum of 1 grammolecule per dm. of said medium.

2. A refrigerating device as set forth in claim 1 wherein said cooling produced by said cold gas refrigerator is controlled in accordance with the amount of condensate contained in said pipe system.

3. A refrigerating device as set forth in claim 2 further comprising an overflow, a receptacle for said overflow, said receptacle being supplied with condensate when said liquid level rises above a certain predetermined height.

4. A refrigerating device as set forth in claim 3 wherein heat is supplied to said receptacle whereby the condensate contained therein is evaporated.

5. A refrigerating device as set forth in claim 4 where- 6 in an element having one end which is at a temperature exceeding that of said condensate supplies heat by conduction to said receptacle.

6. A refrigerating device as set forth in claim 1 further comprising means for reducing the amount of medium in said pipe system during the operation of said cold gas refrigerator.

7. A refrigerating device as set forth in claim 6 wherein said reducing means includes an auxiliary receptacle, two conduits connecting said receptacle to the pipe system, a check valve in one of said conduits, and a stop valve arranged in the other of said conduits, said check valve being operative so that only auxiliary medium can flow to said auxiliary receptacle.

References Cited in the file of this patent UNITED STATES PATENTS 2,527,386 Alsing Oct. 24, 1950 FOREIGN PATENTS 695,857 Great Britain Aug. 18, 1953 

